A device for the serial exchange of data between two stations is described in the report by H. E. Schurk, W. Weishaupt and S. Bourauel "BMW On-Board-Diagnose" (BMW On-Board Diagnostics), VDI Berichte (VDI Reports) No. 612, 1986, pp. 387-401. In the concept presented in that report, an exchange of data takes place between a motor vehicle controller fitted in a motor vehicle and an externally connectable service tester. For data transmission, one data transmission line TXO is used for both transmission directions. However, the data transmission from the service tester to the motor vehicle controller and vice versa takes place with a time offset; temporally parallel transmission in both directions is not possible.